Shock absorber



` July 30, 1935- G. R. PENNINGTQN SHOCK ABSORBER Original Filed Marchll, 1951 2 Sheets-Sheet l w 'Y w Arr-oe/VEK 2 Sheets-Sheet 2 G. R.PENNINGTON SHOCK ABSORBER Original Filed March ll, 1931 July 30, 1935.

Patented July 30, 1935 UNITEDA STATES snoek Asonenn Gordon R.Pennington,

Cleveland Heights, Ohio,

assignor to Pennington Engineering Company, Cleveland, Ohio, accrpcra'tion'of Ohio Application March 11,

1931, Serial No. 521,64

Renewed August 28, 1933 f 21 Claims.

The invention has to do with improvements in shock absorber mechanismsof the hydraulic type. The improvements are especially applicable todouble-acting hydraulic shock absorbers de- 5 signed to control andpreferably to supplement the action of the suspension springs of avehicle, though the invention in some of its aspects is applicable tohydraulic control mechanisms of various kinds, as will be apparent whenthe invention is explained.

The chief object of the present invention, generally speaking, is theprovision of improved valve mechanism for controlling the rloW of theWorking liquid of hydraulic control mechanisms, including shockabsorbers, the specific nature of the improvements being hereinafterpointed out.

Another object of the invention is the provision of a shock absorber ofthe vane or swinging piston type in which axial thrust on the vane is 30eliminated and mechanical frictional Wear minimized.

A further object of the invention is to simplify the construction andboth to simplify and facilitate the manufacture of hydraulic shockabsorbers of the vane type.

Other objects of the invention more or less incidental or ancillary tothe foregoing, together with preferred means for attaining said objects,will be pointed out in the following description.

VThe present improvements lend themselves particularly Well ytoembodiment in hydraulic shock absorbers or control mechanisms havingoperating characteristics similar to those of the shock absorberpatented in my United States Reissue Patent No. 17,409 and of the shockabsorbers disclosed in my copending applications Serial No. 320,413filed November 19, 1928 and Serial No. 496,909 iiled November 20, 1930,and in the accompanying drawings I have shown the invention embodied ina double-acting vane type shock absorber having operatingcharacteristicssimilar to those of the instrument disclosed in the last namedapplication.

In the accompanying drawings, Fig. 1 isa` sectional view of a preferredform of the shock absorber, the section being taken on the broken line Il of Fig. 2. s

Fig. 1a is a fragmentary sectional view showing a slight modication ofthe construction shown in Fig. 1.

Fig. 2 is a Vertical section taken on the line 2 2 of Fig. 1. l

Fig. 3 is a fragmentary section taken on the line 3 3, Fig. 2, showingone of the special features of the construction.

(Cl. 18S-89) Fig. 4 is a fragmentary section on the line 4 4, Fig. 2,showing another feature of the construction.

Fig. 5 is a fragmentary View on an enlarged scale of a portion of thecontrol valve mechanism. Y

Fig. 6 is a fragmentary section on the linel 6 6, Fig. 1.

Fig. 7 is a fragmentary section on an Venlarged scale showing amodication of the control valve 10 mechanism of the instrument showninFigs. 1 and 2. l

Fig. 8 is a section on the line 8 8, Fig. '7.

Fig.9 is a View similar to Fig. .7 of another modiiication of thevalvemechanism.

Fig. l() is a section on the line l0 l0, Fig. 9.

Fig.v 11 is a sectional View showingy still another modification of thecontrol valve mechanism.

Fig. 12 is a section'on the line |2 I2, Fig. 11.

Figi. 13 is a section on a still larger scale showing another modicationof the control valve mechanism.

Fig. 14 is a View similar to Fig. 13 showing still another modificationof the control valve mechanism.

.,Fig. 15 is a diagram representing the cycleof resisting forces set upby the shock ,absorber to relative'movement of the casingand pistonparts corresponding to the movement of the frame and axle parts of thevehicle on which the shock absorber is mounted.

Shock absorbers of the character of those illustrated in the drawingsmay be mounted on a motor vehiclein any of the known ways to control themovements of the chassis frame and vehicle body in relation to theground wheels of the vehicle. Thus, either the casing element 'or thepiston element of the shock absorber may be rigidly connected either tothe chassis frame or to the aXle of .the vehicle While .the otherelement of the shock absorber is connected by suitable crank and linkmechanism to the other vehicle element. The commoner practicev is toconnect the casing structure of the shock absorber to the chassis frameand to connect the piston element by crank and link devices to the axle,and it will be assumed throughout the following description that theinstruments described are to be so mounted. Y

Referring in detail to the constructions illustrated, and rst to theform of instrument shown in Figs. 1 to 6, the casing structure of theinstrument comprises a rear plate-like part l which is circular in form,an intermediate part 2, and a front plate-like part 3. These parts maybe made of any suitable metal, but I prefer to make the back plate I asteel forging and the other parts malleable iron castings. If desired,all three parts may be steel forgings. Still other metals may be foundsatisfactory.

The parallel side surfaces of the intermediate casing part 2 nicely ntthe adjacent plane surfaces of the rear and front parts and the threeparts are tightly and rigidly secured together by cap screws 4, Il anddowel pins 5, 5. The cap screws pass loosely through apertures in thefront part 3 and the intermdiate part 2 and engage threadedclosed-bottom holes in the rear part i. Suitable lock Washers e areprovided between the heads of the cap screws l! and the front plate 3 toprevent loosening of the screws. The doWel pins 5 engage apertures inthe three casing parts with suitable ts for dowel members and serve toaccurately position the three casing parts in relation to each otherwhile the cap screws rigidly clamp the parts together. The rear casingpart I is formed with apertured lugs Ia, Ia to receive the usualsecuring bolts by which the instrument is attached tc the side The whichbar of the chassis frame of the vehicle. casing structure includesadditional parts Will presently be described.

As shown in Fig. 2, the casing part 2 forms the peripheral Wall of vanapproximately sector shape chamber. In this chamber is fitted a swingingpiston or vane 6. The'piston is connected rigidly and preferablyintegrally to a shaft I which extends through the front casing member 3and is rotatably supported in a bearing boss 32 thereof. The rearwardlyextending end of the shaft is rotatably supported in a bearing which isformed by drilling the rear casing plate I and fitting the same with asuitable bearing bushing Il. I prefer to drill entirely through theplate I to form the said bearing aperture and then tightly close theaperture over the end of the shaft 'I by means of a Welch plug 8. Thepiston 6 comprises a vane part proper ISUt and a hub part 6b whichcarries the vane and which is somewhat greater in diameter than theshaft 'I. The peripheral wall of the sector shape chamber of the casingis formed with a hollow cylindrical extension at l!cb to accommodate thehub part 6b of the piston (Fig. 2). The chamber wall at 2*L and theperipheral wall thereof at 2b, the inner planeV surfaces of the vcasingparts I and 3 and the various surfaces of the piston which are adjacentto and cooperate with these casing Ysurfaces are all carefully machinedor finished to aiford Working nts between the piston and the Walls ofthe casing chamber that will prevent undue leakage ofthe Working fluidfrom one side of the piston to the other.

The shaft 'I has its outer end serrated or other- .wise suitably formedto receive the usual crank arm 9 which is adapted to be connected bysuitable link devices (not shown) of Well known character with the axleof the vehicle.

To provide a reserve reservoir for working Auid and at the same timeform a liquid tight closure for the Ventire apparatus, the casingstructure also includes an outer cupped part I which can appropriatelybe stamped or pressed from sheet steel. The casing part Ill is aperturedto t over the shaft I and at its rear open side said casing part isformed with a narrow outwardly turned flange I@nM which engages anoutwardly turned ilange Ic of the casing part I and is secured to thelatter part with a liquid tight joint. Such a joint can be formed invarious Ways, but I prefer to make the connection by forming a welded orbrazed joint II by the use of methods and apparatus known in the art. Ishall hereinafter vemploy the term welded as comprehensive of Welding,bracing, and the like.

To render the joint between the shaft 'I and the casing part Ill vliauidtight, I provide a packing designated in its entirety by the numeral I2.This packing compris-es an annular ring I2, preferably of cork, a ringI2b, preferably of rubber, and a metal ring I2C which is cupped. asclearly shown in l, to embrace the rubber ring I2b and partially embracethe cork ring I2EL so as to control the deformation of these latterrings when they are placed under pressure. Be-

tween the outer peripheral part of the metal ring E2C and the adjacentouter wall of the casing .part 3 is a coil spring IZd which serves tomaintain a moderate pressure on the packing rings. rIhis pressure servesto press the packing rings into close engagement with the shaft andywith each other and also vto press the packing ring I2a into closeengagement with the casing part I3 adjacent the shaft l. VIf it isdesired to rely upon the resilient character of the rubber ring 52', thespring I2d may be omitted.

Y As indicated in Fig. 2, the piston S divides the sector-shape cavityof the casing structure into a chamber A above the iston and a chamber Bbelow the piston; and, as indicated in Fig. 1, a relatively largeirregular chamber C is provided between the cupped outer casing membervto and the inner casing structure made up of the parts I, 2 and 3. Inthe operation of the device the chambers A and B and the reservoir C areoccupied by a body of liquid, such as a suitable oil, which constitutesthe Working fluid of the device. The casing member I@ is provided at itsupper side with a filling aperture having a suitable screw closure Ib toprovide for the introduction of the liquid. In the operation of thedevice the chamber A constitutes a pressure chamber for resisting-theupward movement of the piston El and thus checking rebound of thevehicle springs while the chamber B serves as a pressure chamber toresist the downward movement of the piston 6 to check and control thecompression of the vehicle springs. The liquid controlling devices ofthe instrument by which these functions are accomplished will now bedescribed.

rEhe shaft I of the piston is formed with an axial bore extending fromend to end of the shaft, said bore being designated in its entirety bythe numeral Ia. The bore la varies in diameter in diiferent parts of theshaft as clearly indicated in Fig. l. In that section of the bore 'Iaextending within the piston 6 is fitted-a throat member I3 which isformed with an axial passage that nares from a minimum diameter in themiddle to maximum diameters at its two ends, thus forming a meteringthroat IfL which is most clearly shown in Fig. 5. The throat member I3is preferably made of hardened steel and is forced into position fromthe rear end of the shaft so that it abuts firmly against a shoulder inthe bore 'Ift as shown in Figs. l and 5. The bore la is tightly closedat the rear end of the shaft by means of a plug IA which is insertedwith a forced t against a shoulder formed in the wall of the bore. Theother end of the bore, at the outer end of the shaft l, is tightlyclosed by a screw plug I5. The inner end or side of this other of thestop.

plug is drilled out; to form a recess llia and the resulting annularedge of the plug engages a soit metal gasket i6 which, when the plug isscrewed home, serves to closethe bore with a liquid tight joint. At therear side of the metering throat the piston is formed with a radialpassage i7 extendingfrom the bore 'IEL to the periphery of the hub 6b ofthe piston-so as to communicate with the pressure chamber A, and iniront of the throat the piston is form-ed with a ES extending radiallyfrom the bore la to the periphery oi vthe hub 6b so as to communicatewith the pressure chamber B.` See Fig. 2. For reasons which will bestated later, the end portions of the throat member I3 partially coverthe inner ends of the passagesv I1 and i3. Disposedin the throat I3a isa small steel'ball i9 which, for lack of a better name, is termed ametering valve. As will presently appear, the ball i9 does not functionlike the usual or conventional valve. The ball i9 ts the smallestsection of the metering throat with a small clearance and is free tomove endwise of the metering throat subjectto a iXed stop- Ma formedintegral with the plug ill and a yieldable stop 2G which is slidablymounted in the bore yI3 and isnormally pressed against the shoulder lbof the bore la by the strong coiled spring 2l which is interposedbetween the stop member 2i) and the screw plug l5. The larger portionjoithe stop member 20, which slidably ts the bore la. is formed intransverse section as shown in Fig. 6, the shape being such as to permita iree movement oi the working liquid from one side to the As shown inFig. 5, the ends of the stops Ifla and 2Q are cupped to t the ball i9 toafford relatively-large areas of Contact for it. As will be seen from aninspection of Figs. l and 2, the inner cylindrical surface 2a of thecasing part 2 is formed at .its upper side Vwith two tapered grooves 2Cand at its lower side with two similarly tapered .grooves 2d. One of thegrooves 2C is arranged tovcooperate with the outer end of the passage ilwhile one of the 'grooves '2d is arranged to cooperate with the outerend of the passage 8. The grooves?C and 2d are formed in duplicate toadapt the casing part 2- for use in either a right side or a left sideshock absorber. On reference to Fig. 2, it will be noted that as thepiston swings downward the endoi the passage i3 will be graduallycovered or closed by the cooperative action of the groove 2d; andsimilarly when the piston swings upward the upper endfof the passage l1will be similarly clos-ed by the cooperative action of the groove 2c.

The pressure chamber A at its upper end has direct communication withthe reservoir space C through a very small passage 22 which is formed byscratching a groove in the face of the back plate l of the casing. 'Ivhesizeof the passage 22 is such as to permit the Vfree egress oi anyair-that may enter the chamber A while it prevents'outilow oi' anysubstantialamount of the working liquid. cates at its lo-wermost pointwith the reservoirV C through a passage designated in its entirety as'23(see Fig. 4) and formed in the back plate I. The passage 23 ispreferably formed by al bore Z3a extending from the inner face of theplate l partially through the plate and by a bore 23l0 which extendsfromthe front face of the plate l at an angle to the bore 23a to join therear end of the latter. The front end of the bore 23?- is formed largerthan the other part thereof with a resulting shoulder which `serves as aThe chamber B communis'cat-for a'ball'check valve'Zd. l The, bores 23aand 23b are disposedyasshown in Fig. 4,'so thatthe inner end oftheformer is partially covered by the adjacent .casing part 2 which thusserves to retain the valve 24 in operative position, at the same timepermitting ow of liquid through the passage 23 from the reservoir C intothe pressure chamber B while flow in the opposite direction is preventedby the action ofthe check valve.` 1

On reference to Figs. 2 and 3, it will be observed thatthe back plate Iis formed with a passage ld which `communicates at'one end with thespace between the inner end of the shaft 1 and the closing plug 8 and atits other end communicates with the reservoir space C. This passage Idserves asa drain-toconduct intereservoir C any liquid leaking from thepressure chambers A and B through the shaft bearing of the plate sovthatit is impossible for pressure to accumulate at the inner end of theshaft and 'thus force the latter forward with resultant pressure of lthefront side of the piston against the front plate 3 of the casing,

The shock absorber is prepared for use by filling its working chambersand theu reservoir C with a suitable oil or other working liquid. Thefilling is accomplishedby removing the screw closure I0b and pouring theliquid into the reservoir chamber C, meanwhile moving the crank arm 9 toswing the piston from its lowermost position to its highest position andif necessary repeating this movement several times until it is certainthat suiiicient liquid is drawn from the reservoir C through the passage23 into the lower chamber B and thence forcedi through passage !S, axialbore 'le and passage i1 intotheupper chamber A, so that both chambers Band A are completely lled withV the liquid. Thereservoir C canthen belled with `liquid up to the level of the lling aperture, thus providinga large reserve supply of working liquid. When, in. thisfilling-operation, theV piston 6 is swung from' its lower toits upperposition the chamber B, is

nlled with Vliquid while air in the chamber A Y is forced out throughthe passage 22 intothe reservoirspace C and thence outward through theiilling aperture, vwhile on the downward movement of the pistontheliquid in the chamber B is transferred through the passages in thepiston to the chamber A. movement of the piston, as stated, it isassured that the air is completely driven from the chambers A yaIidB andthat said chambers are completely nlled with liquid. Y v

Before Vdescribing the ,operation of the instrument. in detail, jit maybe observed that while By repeating the with other types ofv shockabsorbers, the construction and operation of the apparatus being suchthat it ofiersa resistance to the nrs-t part of the full compression ofthe vehicle springs which is so slight as to be practically negligible,that, is, unnoticeable to a rider the vehicle,` vwhile after suchinitial N compression of the .spring occurs the resistance to furthercompression afforded by the shock absorbers is automatically increasedrelatively rapidly as such compression proceeds so that a largeresistance is developed to supplement the resistance of the vehiclesprings, the maximum resistance being reached at or near the end of thespring-compressing movement of Ythe parts. On the other hand,the'resistance aiorded by the apparatus to the rebound of the compressedvehicle springs is preferably never equal to the maximum resistance thatmay be opposed to the compression of the springs but in any case has avalue at or'near the normal position of the parts on their movementduring the rebound which is substantially greater than the resistanceoffered to the first part of the springcompressing movement. The cycleof the present instrument (like that of application Serial No. 496,909)has the added feature thatthe rebound resistance, as well as that duringspring compression, is automatically varied.

In the use of my shock absorbers, the vehicle is preferably iitted inthe usual manner with a set of four of the devices, one to control theaction of each of the four vehicle springs.

In Figs. 1 and 2, the piston 6 of the shock absorber is shown in itsnormal or intermediate position corresponding to the normal load of thevehicle with the latter standing still or moving over a smooth and evensurface, and the corresponding position of the crank arm 9, which may beassumed to be connected through a link (not shown) with the axle of thevehicle is also approximately horizontal, the position of the axis ofthe crank arm being indicated by the dot-anddash line D in Fig.` 2. Thenormal positions of the piston and connected parts obviously will varysomewhat with variation of the vehicle load.

In the operation of the device, when the vehicle wheel strikes anobstruction its axle is lifted, the vehicle spring is correspondinglycompressed and at the same time the'crank arm 9 of the shock absorber isswung upward while the piston 6 is swung downward from its normalposition shown in the drawings. As the piston 6 moves downward, theliquid in the chamber B is forced through the passage I8 into the boreI3 and against the metering valve I9, thus moving the latter to the leftout of the more constricted portion of the metering throat I3 andagainst the stop Ida, whereupon the liquid is free tov iiow on throughthe passage I1 and into the pressure chamber A. At the beginning of thedownward movement of the piston 6, the liquid in the chamber B oifersvery little resistance to the movement of the piston because the liquidhas practically unobstructed egress from the chamber B to the chamber Aas described; but after the downward movement of the piston 6 hascontinued for v a certain distance, corresponding to a certaincompression of the vehicle spring, the lower end of the passage I8 willhave moved sufficiently out of register with its cooperating taperedgroove 2d to restrict or throttle the flow of the liquid so that energyis absorbed in this way at an increasing rate as the piston continuesits movement and correspondingly increased resistance to the compressionof the vehicle spring is afforded by the shock absorber. Thus theresistance developed by the shock absorber to the spring compressionautomatically increases as the corresponding movement of the pistonincreases and l that movement increases with the intensity of the forcecausing it, that is to say, with the size of the obstruction and thevelocity with which the vehicle strikes it. I prefer to design the shockabsorber so that it will offer suflicient resistance to the compressionof the vehicle spring to enable it and said spring fully to absorb allshocks that will ordinarily be encountered by the driver of average careand rely upon the rubber bumper with which vehicle axles are equipped tosupplement the shock absorber spring in the case of the rarelyencountered extremely heavy shock.

rHowever, it is to be understood that the shock absorber can be designedto completely supplement the vehicle spring without the use of therubber bumper.

When the upward movement of the vehicle axle in relation to the vehiclebody is ended, the vehicle spring starts to return to its normal loadedform and this so-Vcalled rebound of the spring swings the crank arm 9downward and the piston upward. As soon as this rebound movement starts,pressure is established in the chamber A and liquid starts to iiow fromsaid chamber through the passage I'I into the bore la and thence throughthe metering throat |32 and passage I8 to the lower chamber B of theshock absorber. As soon as the reverse flow starts through the throati321, the ball I9 is drawn into the throat against the stop 20, as shownin full lines in Fig. 5. Thereupon the resistance to the upward movementof the piston G is determined by two factors, namely, (a) the force withwhich the spring 2| holds the stop 20 and consequently the valve I9 inposition against the force of the flow and (b) the position of thepassage I8 in relation to the groove 2d at the beginning of the rebound.Neglecting for the moment the second of these factors, it will be seenthat as soon as the metering valve I9 is positioned in the throat I3aagainst the stop 2i) the pressure in the chamber A will cause at least asmall amount of liquid to be forced through the clearance between theball I9 and the throat I3a and, in case the vehicle spring had beenconsiderably compressed and the rebound force is correspondingly large,the pressure against the ball I9 may be suiiiciently great to force thestop 20 away from the metering throat against the tension of the spring2I, thus moving the ball I9 into the ilaring portion-of the meteringthroat and increasing the effective capacity of the latter toaccommodate a larger iiow of the liquid. The resulting resistance to themovement of the piston 6 obviously is dependent upon the tension of thespring 2l. It is contemplated that this spring when assembled in theapparatus shall be sufliciently preloaded to afford a suitableresistance to movement of the metering valve. This resistance can bevaried in either of several ways, for example, by selecting springs ofdifferent sizes or strength or by varying the degree to which the springis preloaded as by substituting a stop member 2D of different length, orsubstituting a screw plug I bored out to a different depth, or byintroducing one or more thin washers between one end of the spring andits adjacent abutment. The last mentioned expedient is illustrated inFig. la showing the end portion of the shaft structure in which I is theshaft, I5 the threaded plug, 2| the spring and I5b a disk or washerforming an abutment for the end of the spring 2 I'. By removing thescrew plugs I5? and either removing the washer I5b completely orsubstituting for it a washer of different thickness, the preloadedtension of the spring can be varied to the desired degree. In some oneof the ways mentioned, tension of the spring is made such as to afford asuflicient Ylo . has two advantages.

A possible. i v cission ofk the factors involved in the flow of page berA to adequately check the rebound of the vehicle springs. As to thesecond factor above referred to, the resistance to the upward movementof the piston determined by` the tension .of the spring 2l will bemodified if the piston had moved far enough during the compression ofthe vehicle springs to more or less cover the end of the passage IS. Forexample, if the piston had moved `far enough to practically completelycover the end of the passage it it is obvious that the resultantthrottling of the'flow through said passage would in itself stronglyresist the upward movement of the piston and this resistance is added tothat offered by the valve spring 2 E, with the result that the return orrebound movement ofthe piston is slow at the beginning ofthe movementbut lis permitted to pick up speed more and more rapidly as the end ofthe passage i8 is uncovered. When the compression of the vehicle springshas not been great enough so that the downward movement of the pistonclosed off the outer end of the passage i8 to any considerable extent,the resistance to rebound afforded by the shock absorber is determinedpractically entirely by the t-ension of the valve spring 2 l. It will beobserved that the piston hub 6b with its axial passage and radialpassages ll' and i8 and the adjacent wall surface 2a with its taperedgroove 2d serve as a valve adapted to gradually cut off th passage I8 asthe piston moves.

The fact that the throat member I3 partially covers the inner ends ofthe passages ll and i8 One is that the flow of the liquid from thepassages ll and i3 into the bore 'le is rst directed away from thethroat i3@ around the stop projection llla or 2i), as the case may be,with the result that the fiow through the throat member i3 is morenearly on lines parallel to the axis of the throat than would be thecase if the flow from the passages il and i8 into the bore la were notdeflected by the ends of the meinber i3. Because of this uniformparallel flow of the liquid as it passes through the metering throat,there is less tendency for the liquid to force the ball valve 8 againstthe walls of the throat in a manner to cause any undue wear. The secondadvantage is that the partial closure .of the inner end of the passageIS makes it impossible, during assembly of the valve mechanism, eitherduring manufacture or later, for the metering ball i9 to fall into thepassage i3 with resultant annoyance and loss of time. o

It will be understood that the clearance between the ball 9 and themetering throat will, at all times during the rebound movement, afford asmall passage for the flow of liquid past the valve without movement ofthe yieldable stop 2B. This permits the piston i to have short or slowmovementswithout any substantial hydraulic resistance and thus allowsthe vehicle springs to have relative freedom of action in response tothe very small irregularities of road surface. VAt the sametime the sizeof the clearance between the ball valve and the throat is not made greatenough to noticeably diminish the hydraulic resistance of the shockabsorber to expansion movements of the vehicle springs which are oflargerscope or of i great speed.

The form of the metering valve, in conjunction with .the meteringthroat, has the distinct advantage that it makespcssible the use of asmaller or lighter relief spring 2l than would otherwise rbe WithoutundertakingV a complete disthe working liquid'through the: meteringthroat, it may be pointed out that the ow during the re.- boundmovementof the shock absorber isv characterized by distinct advantagesincident tothe form Vof the metering valve. v On reference to Fig. 5, itis obvious. that the metering ball l musthave a very strong throttlingeffect upon the flow with a resultant large drop in pressure from theinlet end to the YoutletendY of the meteringthroat. However, the"pressures to which the metering ball Vitself is subjected are in partdetermined by the form of the ball. The passage between the surface ofthe ball and the walls of the throat is annular and by reason of theshape of the ball the walls of the annular passage converge in thedirection of flow toward a transverse plane through'the center of theball and from that plane then diverge. In other words, we have in effecta sort of annular Venturi tube so that thev flow inthe converging partof the passage is marked by gradual reduction of pressure and increaseof velocity as the above mentioned central transverse plane isapproached. After this central transverse plane is passed, the velocitydiminishes as the cross sectional area of the passage increases. At thesame time, the pressure diminishes because of the very great throttlingeffect of the metering ball but this latter drop in pressure is gradualfrom the above mentioned central plane toward the right. The net effectof the action is that the ball is subjected to Va smaller net pressureon itsinlet side and to a larger net pressure on its outlet side thanwould be the case, for example, if the metering or throttling memberwere in the form of a disk. Consequently, as rabove stated, the form ofthe metering valve makes possible the use'ofa vsmaller or lighter spring2l than would otherwise be'possible. This is a consideration of verygreat practical importance because ofthe limited space available for thespring, particularly in shock absorbers of the smaller sizes. H

A. When relatively soft andflexible suspension springs are employed andthe shock absorber is designed, as preferred, to adequately supplementthe resistance of the springs to compression when obstructions areencountered, the force of `this resistance afforded by the shockabsorber is relatively large at its maximum and the resisting forceafforded by the shock absorberto the rebound of the spring wouldprobably never exceed the said maximum resistance to the compression ofthe spring and ordinarily would at all times be less than said maximumresistance, while vit should, at the time the parts areat or near, i. e.inthe region of, vtheir normal positions, in the rebound movement,materially exceed/the' minimum resistance afforded to the compression ofthe springs. I prefer to make the resistance to movement fof thespringsin the rebounddirection at the timeV the shock absorber parts arein the region of their normal positions decidedly greater than theminimum resistance afforded to 'the com-1 pression of the springsbecause the shock absorbers in this manner add greatly to the lateralstability of the vehicle, or in other words,'greatly resist the tendencyof the body of the vehicle tol rocker sway. rThis feature of theapparatus is of marked importance when the shock absorbersare designedto operate upon a cycle includingthe features of the cycle disclosed inmy aforesaid Patent Reissue No.g17,fl09 since with that cycle ofoperation the resistance of. the shock absorbers to the compre'ssion'ofthe springs when' the parts are-at or near Vtheir normal positionslnustbe soY` small as to be practically unnoticeable in order that theadvantage of thersoft vehicle springs may l be had, and consequently thesaid resistance to the compression of the springs is'not sufcient toafford the lateral stability referred to and it is only by making theresistance to movement of the springs in the rebound direction amplylarge when the parts are at or near their normal positions that thesaidV lateral stability is attained. On the other hand, it is desirablethat the resistance to rebound movement of the piston afforded by thevalve I9 for spring movements of moderate amplitude should not begreater than may be necessary to insure stability of the vehicle body ascomparative freedom of action in the suspension springs is desirable-inthe case of spring movements of moderate amplitude. The operatingcharacteristics of the present instrument make it possible to reduce toa minimum the resistance offered by the spring pressed valve I9 to suchmoderate spring movements for the reason that a relatively large amountof energy is dissipated during both spring compression and springrebound movements of larger amplitude by the throttling action attherend of passage i8, the amount of such energy dissipation beingautomatically varied according to the intensity of the force causingcompression of the suspension springs, and for the further reason thatthe effective resistance of the valve I9 during spring rebound isautomatically increased with increase of the velocity of the flowresisted because of the above described venturi effect. My limprovedmechanism is in a further respect automatic in operation, since thespring-pressed valve I9 which furnishes the moderate predeterminedresistance to movement of the piston in the rebound direction in theregion of the normal position of the piston, is adapted to Ayield underincreased pressures due to increased viscosity of the working liquid.Thus there is automatic approximate compensation for changes inviscosity due to changes of temperature withY the changing seasons ofthe year and with variations in the rate of work performed by theinstrument, so that the resistance to a given rebound movement ofmoderate amplitude is maintained constant. This is an important featuresince the changes in resistance incident to changes in viscosity arelarge enough, in comparison with the moderate minimum resistance whichmust be opposed to rebound to secure stability, to cause a verynoticeable unfavorable eiect upon the riding quality of a vehicle drivenover relatively goodroad surfaces.

In a broad aspect of the invention, my improved shock absorber ischaracterized by means for controlling the, flow of the Working liquidunder pressure which, in the case of suspension spring movements ofVwide amplitude, oiers a resistance to some part of the piston movementcorresponding to compression and rebound of the suspension spring whichis automatically varied to an extent determined by the amplitude of thespring compression movement. and which, in the case of spring and pistonmovements of lesser amplitude, offers to the liquid flow caused byrebound movement of the piston in the region of its normal position amoderate resistance which is automatically maintained substantiallyconstant for a given piston speed notwithstanding variation in theviscosity of the working liquid. The advantage aimed at can be securedin some measure if the resistance which is varied according to thespring movement is interposed only during springy compression or onlyduring rebound. If said resistance is interposed only in one of saidparts of the movement it preferably shouldl be during spring compressionas that makes possible the use of softer suspension springs. However itis best thatthe graduated resistance be interposed in both compressionand rebound movements since this more widely distributes the Work to bedone.

The character of the forces set up in the pressure chambers A and B ofthe preferred form of the device is illustrated by the diagram shown inFig. l5. In this diagram the forces are measured vertically above andbelow the horizontal line or axis x-:Lx The vertical line y-y representsthe normal or static position of the shock absorber piston G andmovement of the piston in either direction from that normal position ismeasured horizontally on the axis :c-ct'. In the diagram, the full linecurve a represents a complete cycle of the piston movement such asoccurs when a wheel of the vehicle strikes an upwardly projectingobstruction. Considering this full line curve and assuming that therelative movement of the parts starts from the normal positionrepresented by the axis y-1, it will be observed that when theobstruction was encountered there was a considerable downward movementof the piston E during which there was a very slight resisting pressureset up in the chamber B, this pressure being represented by thepractically horizontal section a1 of the curve a to the right of thevertical line y-y. However, as the downward movement of the piston 6continued, the outer end of the passage I8, moving opposite the rapidlytapered end oi the adjacent groove 2d, caused a relatively rapid butgraduated increase oi the pressure in the chamber B which is representedby the sharply upwardly curved portion a2 of the curve. The pressurereaches its maximum value at the point a3 near the end of the downwardmovement of the piston 6 and then, as the speed of the piston movementrapidly diminishes, the pressure in the chamber B correspondinglyrapidly falls as indicated by the portion a4 of the curve, the pressurefalling to zero, of course, at approximately the end of the pistonmovement. At this point the rebound movement of the vehicle springbegins, causing a reversal of the movement of the piston G and therapidbuilding up of pressure in the chamber A which is'represented bythe portion a5 or the curve. Since the curve in question represents anextreme compression of the vehicle springs, the outer end of the passageI 8 was completely covered by the downward movement of the pistonrepresented by the portion a2, a3 of the curve, and consequently at thebeginning of the reboundthe pressure in the upper chamber A isdetermined both by the resistance of the valve spring 2I and thethrottling effect incident to the Aclosing orf of the passage I8.However, as

Vthe rebound movement proceeds, the outer end of the passage I 8 comesinto register with the groove Zd and is gradually uncovered and as aresult the resistance to the further movement of the piston isdetermined entirely by the tension of the valve spring 2l and thisresistance is represented by the portion a of the curve. This latterresistance to the rebound of the springs continues with practically nodiminution until the vehicle and shock absorber parts have returned totheir normal positions represented by the line y-y.V The momentum of theparts moved by the rebound or expansion of the springs carriesj saidparts beyond their normal positions and the pressure in the chamber Acontinues but creating the very slight pressure in the chamber` withdiminished intensity as indicated by the section a7 of the curve to theleft of the line y-y, the pressure returning to zero at or near the endof the rebound movement. From this latter point the parts are returnedagain to nor-V mal position, the piston 6 moving downward and Brepresented by the sectiona8 of the curve.

While the full line curve a. which has been described mary be taken astypical, it Will be understood that some parts of the curve or diagrammay vary widely depending upon the character of the obstructionencountered, the speed at which it was encountered and the relativepositions of the shock absorber parts at the same time it wasencountered. For example, if the obstruction represented by the diagrama had been encountered at a substantially higher speed, higher pressuresin the chamber B would have been generated and the section .2 of thecurve would have risen to higher values, such, for example, as arerepresented by the dotted line b2, b3, b4. Again, while the reboundmovement of the shock absorber piston ordinarily terminates, asindicated by curve a, far short of the extreme possible limit or suchmovement, it maybe possible under rare combinations of conditions .for`the rebound movement to continue considerably further and even to themaximum limit. Such an extreme rebound movement `is represented by thedotted curved sections b5, h6 and br in Fig. 15. It will be observedthat the rebound pressure, as represented by the section b5, remainsconstant and equal to the pressure at a, as the movement continues tothe left of the normal axis yy, until the upper end of the passage Il,passing over the tapered groove 2, begins to be closed off, whereupon adecided throttling eiect occurs resulting in the increased pressuresindicated by curve section bfi. Then as the rebound movement is arrestedthe pressure falls to zero again and as the return movement starts, thethrottling action at the outer end of the passage II still continuingthe pressures buildup somewhat as represented by the curved `section b7but gradually decrease as the outer end of the passage I 'I is uncoveredand fall to the very small values represented by the curved section a8asv the piston again returns to normal position. y

The size and taper of the valve groove 2d may be determined empiricallyto suit the conditions of operation. However, the effect of the groove2d can be varied materially by changing the f angular relation of thepiston 6 to the crank arm 9. Thus, if the angular position of the pistonis moved upward inV relation to the crank arm 9, the outer end of thepassage I8 Vof the piston will be covered later in its movement, whileif the position of the piston is adjusted downward the said passage willbe covered 'earlier in its movement.

Similarly, the tension of the valve' spring 2| should be empiricallydetermined in order that the valve I9 may afford the desired resistanceto the rebound of the springs. This determination of the spring tensionshould be controlled, in part at least, by the design of groove 2d andthe corresponding amount of energy dissipated by the throttling actionat the outer end of passage iS occurring during both spring compressionand spring rebound. The greater the amount of energy dissipated in rthisWay the lower the tension of the spring 2| may be made, provided it isnot reduced below the value necessaryfor lateral stability of thevehicle.V When the proper tension of the springv has been determined fora given vehicle, the resistance to a given rebound movement isautomatically maintained at approximately constant value, regardless oftemperature changes with the changing seasons of the year and withvariations in the rate of work performed by the shock absorber, sincethe action of the spring-pressed metering valve automatically adjustsitself to varyingpressures incident to changing viscosity of the workingliquid and thus approximately compensates for variations in theviscosity. Consequently, when the shock absorber is once adjusted tomeet the requirements of a particular vehicle, no further adjustmentsduring service of the apparatus are required.

This latter statement is true regardless of the character of the roadsover which the vehicle may be driven. Thus, while the shock absorbersmay be adjusted, in connection with relatively soft springs, to give asoft, easy ride under boulevard conditions, they will still affordadequate resistance Vand spring control when the vehicle is driven overrough roads because over the smooth roads the amplitude of the vehicleVspring movements is relatively sm-all so that the shock absorbersresistance to spring compression does not come into play, while on therough roads it does come into play and by dissipating relatively largeamounts of energy during the spring compression movement on encounteringobstructions, the work remaining to be done during spring rebound isminimized and, as previouslystated, adequate resistance and control isafiorded even on extremely rough roads. In other words, the operatingcharacteristics ofthe instrument enable it to maintain optimum ridingconditions over a veryr wide range of road conditions. j

This broad or double-range action of the instrument last referred to,whichris due primarily to the'action of the graduated cut-off groove 2d,is helped out to some extent by the venturililze action of the meteringball.' That is to say, the venturi-like action tending to reduce the neteffective pressure on the metering ball andconsequently on the reliefspring 2l, during the rebound movement, increases with the velocity offlow past the metering ball or, in other words, with the volume of oildisplaced by the shock absorber piston per unit of time. Consequently,

while the metering ball, during the rebound movement ofthe shockabsorber, tends to open more widely against the tension of the spring f'been described has a number of striking advantages. It will be apparentfrom an inspection of the mechanism, as shown in Figs. 1,2 and'5, thatthe valve mechanism both from the standpoints of production andoperation is exceedingly simple. It will be observed that a singlepassageway from one side ofthe piston 8 tothe other is adapted, bythejpeculiar two-way act lief spring.

tion of the metering ball and the simple valve action incident to theclosing off of the passage IS when the piston is moved, to provide acontrol of the liquid flow requisite to the relatively complex cycle ofoperations illustrated by the diagram in Fig. 15. The single small ballI9, functioning in the metering throat |393 serves to provide therequisite resistance to the liquid flow during spring rebound and yet isadapted, simply by moving out of the metering throat toward the stopide, to permit a free movement through the metering throat during springcompression.

In additionto the marked simplicity of the mechanism, both structurallyand functionally,

the valve mechanism lends itself especially well to embodiment in thepiston and shaft of a vane type instrument. In the first place, themetering ball i9, because of its form and the manner in which itfunctions, can be made small in size with the result that the hydraulicpressure against it during the rebound stroke of the instrument iscorrespondingly minimized and the relief spring 2| can .therefore be ofmoderate size and strength. Furthermore, the form of the metering bail,because of the venturi-like action previously described, further reducesthe net effective hydraulic pressure onthe ball, thus further favoringthe use of a relatively light re- The possibility of using such a lightspring, as previously noted, is of great practical importance,especially in connection with the smaller sized shock absorbers designedfor use on the smaller motor cars because of the relatively smalldiameters of the shafts in such instruments. y

Obviously the valve mechanism of this character, assembled as it is inthe axial bore of the piston shaft from the vouter end thereof, permitseasy disassembly of the parts either for inspection or renewal or forinterchange of one of the parts, such as the spring 2|, to effect amodification or adjustment ofthe spring action. This construction isimportant in a number of ways. For example, it permits the carmanufacturer to hold the shock absorbers in stock and upon demand adaptthem for cars differing in weight from each other, as in the case ofsedans and roadsters, by an appropriate selection of relief spring 2|.Again, while a given relief spring or a given preloading thereof willprovide a vehicle spring control-for a given car suiting the averageperson, some individual car vowners may desire a somewhat differentcontrol and such desire can readily be met by the simple substitution ofa different spring, or cfa different stop member 2] or a differentclosure plug i5 or a different washer I5b which will give a differentpreloading of the same spring. A further advantage of major importanceincident to the mounting of the relief spring 2| in the shaft of theinstrument, is that the spring can be made of very considerable length,thus making itsaction smooth and uniform for any degree of compressionwithin the working range of the instrument.

The tapered grooves 2c and 2d in manufacture are very readily formed inthe casing part 2 by mounting two milling cutters of suitable diameteron the same spindle. The four tapered grooves can be formedsimultaneously by a single operation, as will be apparent from aninspection of Figs. 1 and 2. By forming the four grooves in this manner,the casing part 2 is adapted to cooperate with the valve passages HandI8 in either a left' side or a right side instrument. For

example, the upper side of the part 2 when it is assembled in a leftfront shock absorber is the lower part thereof when it is assembled in aright front shock absorber. This, of course, is permitted by reason ofthe fact that the part 2 is sym- .metrical about a. horizontal axialplane.

The valved replenishment passage 23 must be at the lower side of theinstrument and the air bleeding passage 22 must be at the upper side ofthe instrument. By forming both of these passages. in one of the casingplates i and 3 the other of said plates, as Well as the casing part 2,can be made universally applicable to both left side and right sideinstruments. In the design of the instrument illustrated, the attachinglugs I, Ia are not symmetrical with respect to the horizontal axialplane of the instrument so that the back plate can not serve either forleft or right side instruments, but when the back plate can be madesymmetrical as to the attaching lugs, as well as otherwise, the passages22 and 23 can be formed in the front plate 3 as shown in my copendingapplication Serial No. 496,909, and then the rear plate can be madeuniversally applicable.

It will be observed that the relief of pressure from the rear end of theshaft l by the drilling of the single short passage ld in the back plateof the instrument is made feasible by the eccentric arrangement of thepiston shaft in the casing structure. f

AY valve mechanism operating upon the principle of that which has beendescribed can be embodied in a variety of forms. For purpose ofillustration, I have shown in Figs. 7 to 14 several differentmodifications of the valve construction illustrated in Figs. 1 and 2,.itbeing understood that in the case of each modification the other partsof the instrument are the same as in the construction shown in Figs. land-2. I shall now briefly describe these modified forms.

In the modification shown in Figs. 7 and 8, the construction in manyrespects is like that of the instrument shown in Fig. 1. The hub part 25of the piston and the shaft 26 are formed with an axial bore 2'!comprising, as an integral part of the piston, a metering throat 21a.This bore is closed at its rear end by means of a cylindrical plug 28which is formed with a stop projection 28a. The outer end of the bore isclosed by a screw plug 29 having a xed stop projection 2.!!a whichreplaces the movable stop 20 and spring 2| of the instrument shown inFig. 1. The stop 29a is made of a length to permit the metering ball 3Uto occupy a position in the metering throat such as to permit themaximum predetermined flow of liquid from the upper pressure chamber tothe lower pressure chamber during rebound of the vehicle spring. As inthe first form of construction, the piston here is formed with aradially extending passage 3| which communicates with the axial bore 2at the inner side of the metering throat and with a radial passage 32which communicates with the axial bore 21 at the outer side of saidthroat. However, in addition the hub of the piston in this modifiedconstruction is formed with radial passages 33 and 34 which are providedwith inwardly closing check valves 33 Vand 34', the passage 33communicating with the-axial bore 2'! at the outer side of thethrottling throat while the passage 34 communicates with the axial boreat the inner side 0f the throttling throat.

In the operation of this modified construction, the action in generalissimilar to that of the instrument shown in Fig. 1 but differs from thelatter in that the maximum resistanceafforded to the rebound of thevehicle springs will vary with the viscosity of the workingliquid sincethe stopV 29a, determining the operative position of the metering valve36, is fixed. In addition, Ythe provision of the extra radial passage 33insures a free flowV of liquid from the axial bore 21 to the lowerpressure chamber of the shock absorber regardless of the angularposition of the passage 32, so that'any throttling of the ow through thepassage 32 by the groove 2d cannot affect the pressure generated in theupper Working chamber of the instrumentI during spring rebound. On thecontrary, the pressure in the upper chamber in the instrument isdetermined entirely by the action of the metering ball 30. Similarly, ifthe rebound movement should go'as far as the instrument will permit soas to close oi the outer end of the passage 3| there Will be no.eilective throttling of the flow from `the lower pressure chamber tothe upper pressure chamber when the return movement starts since a freeflow at that time will be aiorded through the passage 32, bore 21 andpassage 34 independently of the passage 3|. In other words,l the'diagramshown in Fig. `15 will represent thelpressure set up in the instrumentthroughout the cycle of Yoperations except that a curve section shown bydotted lines at c will be substituted for the full line section a5 whilea curve section c'I will'be substituted for the curve section b7. With amodification such as that last described, adjustment oftheinstrumentto'vary the rebound resistance can be eiected by substituting stops 29,29a of different lengths so as to Vary the metering action of the valve.Y

In'the modification shown in Figs. 9 and l0, the hub 35 and shaft V36of' the piston are formed withan axial bore 31 in which is mounted aseparatepmember 38 which'is formed with an axial passage 38a which isshaped to form the metering throat 38h. The member 38 isV securedrigidly against a shoulder in the axial bore of the piston by a screwplug 39 which is formed with'a'stop extension 39 to engage the meteringyball'4ll and limit its movement in one direction. The movement of thesaid ball in the opposite direction is limited by a stop rod 4I whichisadjustably mounted in the outer end of the shaft 36. In the threaded endof the bore 31 is mounted'a packing box 42 which. is engaged by athreaded part of the stop 4|. A gland 43 and packing insure a liquidtight joint between the member 42 and the stop rod. Thesquaredprojecting end 4W of the stop rod can be engaged to adjust it asdesired. The hub of the piston is formed with a radial passage 45 whichcommunicates at its inner end with an annular recess in themember 3S,which recess in turn communicates through radial passages with the axialbore 38a.I Similarly,

the piston hub is formed' with a radial passage 46 and a second radialpassage 41 fitted with an inwardly closing check valve 41. The inner`end of the passage 46 opens adjacent the conical wall of the member 31in such 4a manner that liquid owing inward through the passage 46 mustflow in a circuitous passage before entering the metering throat 38",thus insuring that the flow of liquid radially inward through thepassage 46 and thence through the throat 38b will be along substantiallyparallel axial lines .Y asl it passes through the said throat. a' y Theoperation of this last described modication is, generally speaking, thesame ask that `of the modication shown in Figs. 7 and 8 but differs inthat the functionA performedby the passage `34 and check valve 34 in themodification in Figs. 7 and 8 is absent in the last describedmodification. Y Theoperation of the latter dilers in detail inthefurther respect that the flowfof the f liquid through the meteringthroat 38b is more nearly on lines parallel to the axis of said throat,as in the construction shown in FE. l. Thus liquid iiowing radiallyinward through the` passage 45 nrst enters' the peripheralcircumferential groove in the member 38 and thence passes throughseveral radialpassages into the bore 38a lso thattheilow in the latterboreis evenly distributed. Similarly, liquid flowing radially inwardthrough the passage 46 is deilected by the outwardly' flaring end of themember 38 as the liquid enters thebore'31`so that the flow is uniformlydistributed as it passes from the said bore 31 into the metering throat38h. a

V'With thestop 4I adjustably mounted as described, it is' possible toeasily and quickly vary the resistance o'ered to spring rebound, as willreadily be understood.

1Inthe modification-shown in Figs. 11 and 12, the hub 48 and shaft 49 ofthe piston are formed with an axial bore 50 which comprises a meteringthroat- 50a, just as in the first described con'- structionexcept Vthatthe metering throat is formed as an integral part of the piston; The hubofthe piston is also formed With radial passages 5l and 52 communicatingwith the axial bore 50 on opposite sides of the throat 56a and inaddition there are radially extending passages 53 and 54 provided withinwardly closingv check valves 53 and 54. In the throat 50a is arrangeda ball `metering v alve 55 which is engaged on the rear side by averylight coil'spring 55 which is supported by a closure plug 51 in therear end of the axial ybore 55. rIhe 'spring 56 acts to press the ball55 against the stop member 58, which is like the corresponding part ofthe first described construction. Said stop member is slidably mountedinv the axial bore 50 and is yieldably pressed against the shoulder 5l!bthereof by a relatively heavy coil spring 58 which, at its outer end, isengagedY by an abutment plate v60 that` can be ad- 'justed to varythetension of the spring byv means of the screw 6l. `This screw isthreaded into a threaded packing box 62 which is mounted in the outerend of the shaft with a liquid tight joint. The joint between 'the screw6l and the Ybox 62 `is made liquid tight by means of. a packing 63`andto yield when thefpressure against the metering 'valve 55 during reboundof the vehicle spring exceeds a predetermined value. The Vcoiled springr56`is so light as to permit the metering valve 55 to move relativelyfreely out of the metering throat against the pressure of the springYduring `the downward movement of the piston. Y

In the modification shown in Fig. 13 the meter- Ving valve 65 is formedwith a stem 66 which extends loosely throughthe main member 61 of theyieldable stop. The stop member 61 is formed on its outer end with athreaded nipple 61EL to which is secured an elongated cap member 61bwhich limits the outward movement of the valve stem Said stem at itsouter end is formed with a head 668L and between the latter and thenipple 61a is arranged a light coil spring 68 Whichtends to hold thehead of the valve stem against the outer end of the cap 61". K Y j l Thehub of thepiston is formed with passages 69 and l0 which communicatewiththeaxial bore of the piston at opposite sides of 'the'meteringthroat 'll and the relatively heavy coil spring 12 serving to press thestop member 61 against the shoulder in the axial bore at the inner sideof said stop member. T3 serves as a limiting stop for the metering valveas in the first Vform of construction.

In the operation of the last'described modification, the metering valveis normally positioned in the metering" throat H by the light spring 68in the position occupied by said valveat the begin'- ning of thereboundv movement.v If the rebound movementis suiciently rapid orsurliciently' large the liquid pressure on the valve 65 is transmittedthrough the stem 66 to :the stop member '61, which in turn is forcedagainst the heavy spring 82 causing the latter to yield more'or lessaccording'to the intensity of the pressure. During the springcompression movement of the piston, the unbalanced pressure incident tothe liquid flow. from the lower working chamber of theshock absorberthrough the passage 'l0 and into the axial bore causes the valve 6.5,tomove the left against the tension of the spring 58 until "the passagethrough the metering throat is `quite free, the light tensionA of thespring 68 readily permitting such movement. The xed, stop 13 visprovided so that in case of a very sudden severe pressure on theA valvethe light spring B8 will notbe unduly compressed.

In the last modification, shown in Fig. 14, the metering valve ismounted xedly in the piston while the metering throat is made axiallymovable', thus indicating thatthe essential thing is relative movementbetween the valve and throat. v In'Fig. 14, the axial bore 'i4 of thepiston is formed with a cylindrical contracted portion 'Mil in which athroat member 'l5 is mounted with a` close sliding' fit, the bore ofyth'e'member'lS being shaped to form a metering throat 15a of -thesamecharacter as the Vmetering throats provided in the other forms ofconstruction. The outer end of the throat member 'l5 is engaged by anannular ring 16 which in turnv isengaged by the heavy coil spring l?,the latter thus serving .to press the ring 'l5 against ythe shoulder Mbofthe vbore 14. The inner end of the bore 'M Vis closed by a threadedplug 7S, an extension of which 'carries :the metering vali/e719. A lightcoil spring 80' is interposed between the plug 18 and a ring 8l whichinturn bears against the innerend of the throat member Z5.` The hub of thepiston isfo-rmed with radial passages 82 and 83 which communicate withvthe axial bore at the opposite ends of the throat member 15, thelatterbeing formed at its inner vend with a series of holes '15b toafford free access of liquid to the metering throat. With respect to-vthe other parts of the instrument not shown in as in the cases of theother modifications of Figs'.

7 to 13, it is to be understood that` the construcf permitting apracticallyiree passage of the'gliq'uid.

`past the` metering valve 1.9 tothe upper pressure chamber of the shockabsorber vinsofar as Ythe metering valve is concerned. On the return orrebound movement, the pressure in the upper .chamber of the shockabsorber causes flow from said chamber through the passage 82 into thevaxial bore ofthe piston and this promptly causes movement ofthe throatmember 'l5 to the right against the v'stop ring 16 and, if the pressurerises sufficiently high, the tension of the spring 'l5 will be yovercome`and a suiiicient 'movement of the throat member' vl5 to the right fromthe position shown rin Fig. 1i will occur to limit the resistance to therebound to the desired or predetermined value. It will be observed that,whereas in the previous forms of construction the normal position of themetering valve is slightly to the right of the narrowestsectionof themetering throat, in the last form of construction the normal position ofthe metering valve is slightly to the leftof the narrowest section ofthe throat. The result is that in all cases a minimum relative movementbetween the metering valve and the meteringv throat is required duringrebound movement ofthe shock absorber piston.

Inthe various forms of the valve mechanism which have been described Ihave shown several different forms of stop device for limiting ordetermining,,theposition of the metering valve during rebound movementof the shock absorber, but it Ywill beunderstood that the constructionof ythe instrument inthis respect, as in others, may be subject tovarious other modifications without departing from the; invention asdened inthe appended claims. For example, it will be obvious that in theinstrument shown in Fig. 1 the length of the stop portion M may bevaried in rlength tovary the extreme position of the metering ball and.thereby control the amount (3f-resistance to ythe liquid flow, shouldit for any reasonV be `desirable to have a substantial resistance toliquid flow from the chamber B to the chamber A. And similarly, thatVportion of the stop member 20 between the metering ball and the stopshoulder Tb can be varied in length for asimilar purpose. It 'will alsobe obvious that .the stopmember29a in Fig. 7 or the stop member'dl inFigf.9 may be made of material having a high coeiicient of expansionincomparison with iron or steel such as ebonite as described in Vmyapplication Serial No. 320,413 above referred to;r:, or the ,said stopmembers 29a and 4| may have a composite construction of the characterdisclosed in FigsfBO to 35, inclusive, of the last named application tosecure as large a degree of thermal expansion as may be desired. Asfurther exemplifying possible modifications of the instrumentsillustrated, it will be apparent that the kmetering valve mechanism neednot be mounted in the piston shaft but can be mounted in the'casingstructure.y Obviously, too, my improved meteringl valve mechanism isreadily applicable to 'shock absorbers or other hydraulic control"mechanisms of the reciprocating piston type. Without mention of furtherexamples, it will be understood that the various features of theinstruments described can be modied in various ways without departingfrom the invention as dened in the appended claims.

1.4 VIn a double-acting hydraulic control mechanism, the combination ofa structure having two pressure chambers therein for working liquid; a`conduit interconnecting said chambers, the walls of said conduitcomprising a portion constricted to form a metering throat; amovablemetering member adapted to move in the throat lengthwise thereoflwith a minimum clearance small enough to oiier a strong resistance toliquid ,ilow through the throat; and means for limiting the movement ofVthe movable metering member lengthwise of ther throat, said `means beingadjustable and adapted to hold the movable member against the iiow inone direction in any one of several positions to oler high resistance tosaid ilow and said means also being adapted to permit movement of themovable member to a position in which it oiers a lesser resistance toiow in the reverse direction through the throat.

2. In a double-acting hydraulic control mechanism, the combination of astructure having two pressure chambers therein for Working liquid; aconduit interconnecting said chambers, the walls of said conduitcomprising a portion constricted to form a metering throat; a meteringball movable in the throat lengthwise thereof with a minimum clearancesmall enough to offer a strong resistance to liquid flow through thethroat; a stop vfor limiting the movement of the ball in one directionto hold the ball against theliquid flow in that direction through thethroat in a position to oier high resistance to said flow; anda stop forlimiting the movement of the ball in the reverse direction adapted tohold the ball in a position in which it offers a lesser resistance toliquid ow through the throat in said reverse 4direction than in theother direction.

3. In a double-acting hydraulic control mechanism, the combination of astructure having two pressure chambers therein for working liquid; aconduit interconnecting said chambers, the walls of said conduitcomprising a portion constricted to form a metering throat and saidwalls being constructed and arranged to direct liquid llow through thethroat on linesparallel to the axis thereof; a metering ball movable inthe throat lengthwise thereof with a minimum clearance small enough tooier a strong resistance to liquid ilow through the throat; a stop forlimiting the movement of the ball in one direction to hold the ballagainst the liquid flow in that direction through the throat in aposition to offer highA resistance to saidilow; and a stop for limitingthe movement of the ball inthe reverse direction adapted to hold theballV in a position in which it offers a lesser resistance to liquid owthrough the throat in said reverse direction than in the otherdirection. n

. 4. In a double-acting hydraulic control mechanism, the combination ofa structure having two pressure chambers therein for working liquid; aconduit interconnecting said chambers, the walls of said conduitcomprising a portion constricted to form a metering throat; a vmetering.ball movable in the throat lengthwise thereof with a minimum clearancesmall enough to oiiier a strong resistance to liquid ow through thethroat; a stop for limiting the movement of the ball in one direction tohold the ball against the liquid iiow in that direction through thethroat nism', the combination of 'a structure having-two pressurechambers therein for `working liquid;

cation between said chambers; 'a' movable metering member in saidconduit controlled by the liquid ilowtherethrough and adapted to-oirer alargeresistance to liquid flo-w in one direction through the conduit anda lesser resistance to flow inthe reverse direction through the conduit;and means'independent oi the metering means and controlled by movementof the piston means to offer a variable resistance to the liquid iiowthrough the conduit in the last named direction. g

6. In a double-acting hydraulic "control mechanism, the combination ofYa structure having two ressure chambers therein for working liquid;means comprisinga conduit aircrding communication between the pressurechambers, the walls of said'conduit comprising a section constricted toform a metering throat; a metering ball movable in the throat lengthwisethereof with a minimum clearance small enough to offer a-strongresistance to liquid iiow through'the throat; a stop for'limiting themovement of the ball in one direction to hold the ball against theliquid flow in that directionl through the throat in a, position tooffer a high resistance to said ilow; a spring for holding the said stopyieldingly in position, said spring being adapted to yield when vthe`force of the flowwagainst the ball exceeds apredetermined value; meansfor limiting the'movement of the ball in the reverse direction adaptedto hold the ball in a position in which it oiers operationwith the wallor the duct, forming an annular'venturi-like passage for the flow of theliquid past the metering ball; and means adapted eiectively to hold theball against the yliquid flow inrlon'e direction through the ductthroughout a predetermined range of liquid pressures again'strthe balland, by yielding, to permit movement of the b alllengthwiseof Athe ductwhen the liquid pressure rises Vabove the said range, said meanscomprising a spring and rigid abutments for maintaining the springundertension.

8. In a double-acting hydraulic shock absorber, the combination of acasing structure having a sector-shape working chamber for a swingingpiston; a swinging piston comprising a hub portion mounted in saidworking chamber and dividing the same into two pressure chambers, thehub portion of the piston being formed with an axial bore ant two radialpassages indifferent planes extending from 'the axial-boretothe-periphery of the hub portion of the piston; a tubular meteringthroat member mounted in Vthe axial bore of the piston with oneendthereof partially covering one of rthe radial passages; a metering balloperatively mounted in the metering throat; and ra removably mountedstop member for engagingthe metering ball and limiting its movement 35less resistance to liquid ilow through the throat in the throat towardthe last named* radial passage. Y

9. In a hydraulic control mechanism, the combination of a casingstructure having a sectorshape working chamber therein for a swingingpiston, said structure comprising parallel front and rear walls and aperipheral wall of the said chamber and a cupped outer casing partcovering one of the parallel walls and the peripheral wall with anintervening reservoir space and secured to the other of the parallelwallswith a liquid tight joint; a swinging piston mounted in the workingchamber of the casing; a-shaft to which the piston is connectedextending through one of the parallel wall parts of the casing with abearing support therein and having a bearing support in the oppositeparallel wall of the casing, the said shaft and bearings being disposednear the peripheries of the parallel walls of the casing structure; andmeans affording communication between the last named shaft bearing andthe reservoir space comprising a passage formed in the parallel wallpart in which the said bearing is formed.

10. In a hydraulic shock absorber adapted for use on one side of a motorcar, the combination of a casing structure having asector-shape Workingchamber therein for a swinging piston Aand comprising parallel front andrear wall parts and an intermediate part forming the peripheral wall ofthe said chamber including a cylindrical wall of large radius to engage`the outer side of the swinging piston and a cylindrical wall of smallerradius to engage the cylindrical hub portion of the piston; a swingingpiston mounted in the casing and dividing the sector-shape chamber intotwo pressure chambers, said piston having a conduit formed in the hubportion thereof to afford communication between the two pressurechambers at opposite sides of the piston, the intermediate casing parthaving that portion of its wall formed on the small radius provided witha tapered `groove arranged to cooperate with one end of the conduit inthe piston to gradually close and open said conduit as the piston swingsin opposite directions, and also provided with a second similarlytapered groove that is normally idle but which is adapted to cooperatewith the end of the piston conduit when the intermediate casing part isassembled inV a shock absorber adapted for use on the opposite side ofthe motor car. n

V 11. In a double-acting hydraulic control mechanism, the combination ofa structure having two lpressure chambers therein for working liquid; 4aconduit interconnecting said chambers, the

walls of said conduit comprising a portion constituting ra meteringthroat; a metering member movably tting in the throat to permit movementof one of said metering parts relative to Ithe other lengthwise of thethroat, Vthe throat and metering member being formed to offer a,resistance to the flow of liquid through the throat Y variable with thechange of relative position of the metering member in the throat; means.for limiting the relative movement of the metering member and throat inone direction length- Wise of the throat to oiTer a predetermined highresistance to the liquid flow in lone direction through the throat, saidmeans comprising a movable stop device to hold the movable metering partagainst said liquid iiow, rigid means for `accurately positioning thesaid stop device lengthwise of the throat, and yieldable means againstthe pressure `of the said liquid flow and for permitting movement of thestop device in the direction of said flow lunder a predetermined liquidpressure against the movable metering part; and means lfor limiting therelative movement of the throat and metering member in the reversedirection lengthwise of the throat to permit their relative movement toa position in which a lesser resistance is offered to the liquid iiow inthe reverse direction.

l2. In a hydraulic control mechanism, the combination of a structurehaving a pressure chamber to contain working liquid; a duct throughwhich liquid can flow from and into said chamber, the walls of said ductcomprising a portion constituting a metering throat; a metering membermovably tting in the throat torpermit movement of one of said meteringparts relative to the other lengthwise of the throat, the throat andmetering member being formed to offer a resistance to the ow of liquidthrough the throat variable with the change of relative position of themetering member in the throat; means for limiting the relative movementof the metering member and throat in one direction lengthwise of thethroat to offer a predetermined high resistance to the liquid liow inone direction through the throat, said means comprising a movable stopdevice to hold the movable metering part against said liquid iiow, rigidmeans for accurately positioning the said stop device lengthwise of thethroat, and yieldable means for holding the stop device in such positionagainst the pressure of the said liquid flow and'for permitting movementof the stop device in the direction of said flow under a predeterminedliquid pressure against therrnovable metering part; and means forlimiting the relative movement of the throat and metering member in thereverse direction lengthwise of the throat to permit their relativemovement to a position in which a lesser resistance is offered to theliquid flow in the reverse direction.

13. In a hydraulic control mechanism, the combination of a structurehaving a pressure chamber to contain working liquid; a duct throughwhich liquid can flow from and into said chamber, the walls ofsaid ductcomprising a portion constituting a metering throat; a metering membermovably tting in the throat to permit movement of one of said meteringparts relative to the'other lengthwise of the throat, the throat andmetering member being formed to afford an annular venturi-'like passagefor the liquid past the metering member and toroifer a resistance to theflow of liquid through the throat variable with the change of relativeposition of the metering member in the throat; means for limiting therelative movement of the metering member and throat in onedirectionlengthwise of the throat to oiler a predetermined highresistance to the liquid ilow in one direction through the throat, saidmeans comprising a movable stop device to hold the movable metering partagainst saidvliquid flow, rigid means for accurately positioning thesaid stop device lengthwise of the throat, and yieldable means forholding the stop device in such position against the pressure of thesaid liquid flow and for permitting movement of the stop device in thedirection of said flow under a predetermined liquid pressure against themovable metering part; and means for limiting the relative movement ofthe throat and metering member in the reverse direction lengthwise ofthe throat to permit their relative movement to position in whichyalesser'resistance is offered` to the liquid iiow inthe reversedirection.A f.

14.V In a double-acting hydrauliccontrol mech,-`

anism, the combination ora` structure having two pressure chamberstherein f or Working. liquid; a conduit interconnectingv said chambers,the4 walls of said conduit` comprising a portionA constitutinga meteringthroat; Valmovablepme'-, tering member disposed inthe throat to movelengthwise thereof, the throat and metering member being formed to offera resistanceto the flow of liquid through-the throatvariable Vwith thechange of, positionvof the metering member'in the throat; a yieldablestop Adevice adapted effectively to hold-theA metering member'. againstthe liquid ow in one direction through the throat. throughout apredetermined range of liquid pres--A sures against the metering member;and means for limitingthe movement oi the metering mem-y ber in thelreverse direction in the throat'adapt'ed to permit movement ci saidmetering member to .a position in which it offers a lesser resistance toliquid iiow in the reverse direction.

15. In a double-acting hydraulic control mechanism, the combination of astructure having two pressure chambers therein for working liquid;piston means movable in said pressure chambers; means comprising aconduit affording communication between said chambers; metering meanscomprising a member movable in said conduit and controlled by the liquidflow therethrough, said metering means being adapted to oder a largeresistance to liquid ilow in one direction through the conduit and alesser resistance toA ilow in the reverse direction through the conduit;and means independent of the metering means and controlled by movementof the p-iston means for offering to the liquid low through the conduitin the said reverse direction a resistance variable with the extent ofsaid movement.

16. In a hydraulic control mechanism, the combination of a structurehaving a pressure chamber to contain working liquid; a duct throughwhich liquid can flow from and into said chamber, the walls oi said ductcomprising a portion constituting a metering throat; a movable' meteringmember disposed in the throat to move lengthwise thereof, the throat andmetering member being formed to offer a resistance to the flow of liquidthrough the throat variable with the change of position of the meteringmember in the throat; a yieldable stop device adapted effectively tohold the metering member against the liquid flow in one directionthrough the throat throughout a predetermined range of liquid pressuresagainst the metering member; and means for limiting the movement of themetering member in the reverse direction in the throat adapted to permitmovement of said metering'member to a position in which it offers alesser resistance to liquid ilow in the reverse direction. e

17. In a hydraulic control mechanism, the combination of a structurehaving a pressure chamber to contain working liquid; a duct throughwhich liquid can now from said chamber, the walls of said ductcomprising a portion constituting a metering throat; a metering membervmovably tting in the throat to permit movement of one of said meteringparts relative to the other lengthwise of the throat, the throat andmetering member being formed to offer a resistance to the flow of liquidthrough the throat variable with the change or" relative position of themetering member in the throat; and means for limiting the relativemovement of the metering member and throat saidvstop device lengthwise of thethroat, and l yieldable means forholdingthe stop device-in suchposition against the pressure ofr the liquid flow and for permittingmovement of the stop device inthe direction of the ow under apredetermined liquid pressure against the movable metering part.Vv

. r8.v1n`a-.hydraulic control mechanism, the combination of a structurehaving a pressurechamber to contain workingliquid; a duct throughwhichliquidcan flow from `said chamber, the wallsr or said ductcomprising a portion constituting a metering throat; a metering membermovably fitting in ythethroatto'permitmovement ofi one of Asaid meteringparts` relative to the other` lengthwiseof the throat,y the throat andmetering member being formed to afford an annular venturi-like passagefor the liquid past the metering member and to offer a resistance to theflow of liquid through the throat variable with the change of relativeposition of the meteringmember in the throat; and means for limiting therelative movement of the metering member and throat in one directionlengthwise of the throat, said means comprising a movable stop device tohold the movable metering part against the' flow of liquid from thepressure chamber through the throat, rigid means for acciuatelypositioning the said stop device lengthwise of the throat, andyieldalole means for holding the,Y stop device in such position againstthe pressure of the liquid iiow and for permitting movement ofthe stopdevice in the direction o the iiow under a predetermined liquid pressureagainst the movable metering part. e

i9. In a hydraulic control mechanism, the combination of a structurehaving a pressure chamber to contain working liquid; a duct throughwhich liquid canriiow from said chamber, the walls of said 'ductcomprising a portion constituting a metering throat; a metering ball inthe said throat, said ball and throat forming an annular venturi-likepassage for the ow of theV liquid past the ball-and being adapt-ed tooder a resistance to the flow of liquid from the pressure chamberthrough the throat variable with the change of position of the balllengthwise of the throat; and means for limiting the movement of theball lengthwise ofthe throat in the direction of the said flow, saidmeans comprising a movable stop device, rigid means for accuratelypositioning the saidstop device lengthwise of the throat, and yi-eldablemeans for holding the stop device in such position against the pressureof the liquid flow and for permitting movement of the stop device in thedirection of the flow under a predetermined liquid pressure against theball.

20. In a hydraulic control mechanism, the combination of a structurehaving a pressure chamber to contain working liquid; a duct throughwhich liquid can flow from said chamber, the walls of said ductcomprising a portion constituting a metering throat; a metering membermovably y ment ofthe metering member and throat in one directionlengthwiseof the throat, said means comprising a spring4 and fixedabutmentsfor maintaining the spring undertension, said spring beingadapted by yielding; toL permit movement of the, movable metering partin the direction of the iow when the liquid pressure against the movablemetering part rises above a predetermined value. Y

2l. In a shock absorber vfor controlling relative movements of aroad-supported vehicle part and a second vehicle part supported by meanscomprising a suspension spring, the combination of a casing adapted .tohold a body of liquidV and to f be secured to one'of said vehicle parts;liquidforcing means in the casing comprising a chamber and a pistonmovable in the chamber; pistonactuating means extending to the exteriorof the casing 'and` adapted to be connected to therother of said vehicleparts; conduit means for conductbound of the suspension spring; andmeans for controlling the ow through said conduit comprising a meteringdeviceforming a restricted passageway and' adapted to offer to themovement of thepistonin the rebound direction in the region of" itsnormal position a moderate resistance that is substantially constant fora given piston speed notwithstanding,variations intheV viscosity of theWorking liquid and separate flow control means in seriesrelation-to themetering device for automati'cally varying the effective capacity of thesaid conduit to increase the resistance to the movement of the piston inthe rebound direction toward the region ofl its normal position withincrease in the intensity vof, the force causing relative movement ofthe two vehicle parts.

GORDON R. PENNINGTON.

CERTEFESATE 0iT QORRECHON.

Patent No. 2,609,673. July 30. 1935.

GGRDON R. PENNINGTON.

lt is hereby certiiie that error appears in the printed specification ofthe above numbered patent requiring correction as follows: Page 4,second column, line 74, after tire enrnrna insert ine Words and commaand preferably by selecting a springr 2i of suitable sim; page 5, firstcolumn, line 74-75, for "discission" read discussion; and second column,lino 55, Strike out the second comma; page 10, first eoinmn, line 27,aiter "move" insert the word to; and that the said Letters Patent shouldbe rend with these corrections therein that 'the saine may conform tothe record o the ease in the Patent ice.

Signed anni sealed this 8th tiny oi ctober, A. D. 1935.

Lesl i@ Frazer (Sei-il) Acting Commissioner of Patents,

